I don't have a good tactic for this, but what I did was put Stan's in my tube.
- deflate tube
- unscrew and pull out core
- rotate so the valve is at the bottom
- Squeeze an ounce or two of Stan's into the tube.
- slowly rotate valve to top position.
- Reinstall core.
- Inflate with valve at the 12 O'Clock position.
Every time you reinflate, the valve has to be at 12:00. The Stan's will last for a couple of months. The tube will be a lot slower to lose pressure.